Are you are investigating options to tweak your bike - new stem, seat adjustment
- to make it more comfortable? Are you considering a new bike? Or maybe just
planning on a bike trip and need to order a rental bike.

I. Sizing for a rental bike (prompted by a question from a friend). The following
2 links answer the question.

First, the size
of the frame you need. It has the sizing for road bikes as well as mountain
bikes. (Look at their tip on measuring leg length, and be sure to keep the
book "square" on the wall so that the upper edge is parallel to the ground).

Making a Bicycle
Fit - more detail than you might want about what goes into
a good bike fit. Self described as a "treatise to help set up a road bike
properly, either for racing, touring, or more relaxed riding."

An excerpt from an article on the web site of Malcolm Firth -
Senior Coach, Association of British Cycling Coaches that may help to answer
some of your questions about leg length and seat
angles. His suggestions are based on analysis of data he gathered from various
sources.

".......The two main measurements required for a correctly sized road frame
are the seat tube and top tube lengths. These, together with the seat tube
angle are the parts of the frame most influenced by your body size. Top
tube length is generally taken to be the horizontal distance from the
center line of the head tube to the center line of the seat tube, whilst
seat tube length is the straight line distance from the center of the
bottom bracket to the center of the junction between the seat tube and the
top tube.

To estimate the correct seat tube and top tube lengths for your road bike
several measurements of your body and limbs will need to be taken. The
first of these is your inside leg measurement. This is taken with you in a
standing upright position, without shoes and with your feet about 25cm
apart. The measure is then taken vertically from floor to crutch (the point on
the crutch where the measurement is taken from is the bony protuberance known as the
ischial tuberosity - the lowest part of the
pelvic bone - that you sit on). The seat tube length is calculated as being
2/3rds of your inside leg measurement. Thus, if your inside leg measurement
was 84cm, the seat tube length would be 56cm.

The top tube length of your bike should be proportional to a combination of
your trunk length and arm length. For these measurements you need to be
seated with your back pressed firmly against an upright surface such as a
wall. Trunk length is measured from the seat you are sat on to the top of
your shoulder with you sitting fully upright. The forearm length is
measured from the back of the elbow (with the back of the elbow pressed
against the upright support and with the forearm horizontal) to the centre
of your clenched fist. Total arm length is obtained with your arm straight
out in front and measuring from the upright support to the centre of your
clenched fist (keep your back firmly against the support). The measurements
are used in the following equation: top tube length = 75.25% trunk length +
7.8% forearm length + 7% total arm length - 1cm. The answer should be
rounded out to the nearest 1/2cm.

For the seat tube angle you first of all need to measure your thigh and
lower leg lengths. Thigh length is measured horizontally from the upright
support to the front of your kneecap, whilst the lower leg length is
measured from the top of your kneecap vertically to the ground. Then
calculate the seat tube angle as: Cosine of 26.4% (thigh length / lower leg
length). The answer should be taken to the nearest 0.5 degree.

It is worth remembering that the calculations used to estimate frame size
are generalizations based on average figures calculated from measurements
on a wide range of riders. Within those averages there are variations
typical amongst a group of people. Therefore, no formula can give the
perfect frame size and riding position for every rider. The final, and most
important check will be for you to try out the position you have arrived at
during several rides of increasing distance and severity. Only then can
your riding position be given the fine tuning that will be needed to make
it the best one for you........"

Weight distribution

Why the emphasis on frame size? It has to do with both comfort of position and weight
distribution. Weight Distribution. Bicycles handle best when 55% to 60% of bicycle and
rider weight is on the rear wheel and 40% to 45% is on the front wheel. This will
generally produce a comfortable ride and reduce the possibility of overuse injuries.

When too much weight is forward, bicycle control, handling, and safety may be a problem,
especially on descents. The chance of hand numbness, tired arms and shoulders, neck,
shoulder, and upper-back pain is increased. When too much weight is on the rear wheel, control may be
difficult in corners and front-end shimmy on descents is more common.
Weight distribution results from almost all elements of bicycle fit, including pedal
fore-aft, seat height, seat fore-aft, torso angle and reach. In addition to judging the fit by
your level of comfort after a long ride, weight distribution can be checked by weighing
the bike and rider and then seeing what percentage of that weight is on the front wheel
while on a stationary trainer.

And for TALL RIDERS.

"A few other observations. Tall riders generally have longer legs in relation to
their body length than do average height riders. For example, I am currently coaching a
young rider who is 6ft 3ins tall, whereas I am 5ft
9ins. As you can imagine, when we stand his head is much nearer the clouds
than mine. Not so when we sit, there is less than 2ins difference in
sitting height. Of this extra leg length in tall people, the thigh is often
a greater proportion of the total than with average height people. This
means that to get the knee above the centre of the pedal spindle when the
cranks are horizontal, tall riders with very long legs usually have a
shallow seat angle. In the case of your rider it sounds like the ratio of
his thigh length to lower leg length is about 1.3 to 1, whereas the average
height rider has a ratio of about 1.1 to 1 (see "Road Racing" by Hinault
and Genzling). As a contrast, I once met a rider who was 6ft 4ins tall with
a thigh to lower leg ratio of about 0.9 to 1. For him to get his knee over
the pedal spindle he used a seat angle of 75 degrees.

Tall riders with long legs and short bodies can sometimes encounter
problems with backache. For example, a combination of long thigh, shallow
seat angle, short body and the handlebar stem well down in the head tube
can mean a more acute angle between thigh and body when the leg is at the
top of the pedal stroke. For some riders this can put excessive strain on
the muscles on the back of the thigh that help drive the thigh downwards,
leading to backache. I seem to remember Alexi Grewal (the American rider
who won the 1984 Olympic road race) saying that he encountered this problem
and only solved it when he went to a steeper seat angle than had been
previously suggested from his body measurements. This just goes to
illustrate that you cannot go by formulas alone when dealing with
individual riders. They just help you get into the right ball park, after
that you need to find out whereabouts in the ball park suits you best."

From Andy Pruitt(reprinted from www.roadbikerider.com. This may
help you understand why a good bike fit is so important.)

Wind-tunnel tests have proven that being narrow on the bike is much more important
than being low. Most of us can improve efficiency the most simply by keeping legs and arms
in line with our bodies, not splayed into the wind. A handlebar no wider than the
shoulders is key.

Make a fist and measure across the four knuckles. The difference between the top of
your saddle and the top of your handlebar should not exceed this number. An easy way to
check is to set your fist atop the handlebar (vertically, pinky down) and have a friend
eyeball the fist/saddle relationship from a few feet away.

Your most comfortable riding position should be with hands on the brake lever hoods.
This is the "neutral position" from where you can move to the tops near the stem or the
drops. When you get the on-hoods position right, these other locations will be usable, too.

Your reach to the lever hoods should put your wrists in the "handshake position." That
is, a straight extension of your arms, not cocked up or angled down, which can cause
strain and pain.

Your knee bend at bottom dead center of the pedal stroke is a better indicator of
correct saddle height than numbers produced by leg-length formulas. For most riders, knee
bend should be within a degree or two of 30 degrees.

To get the correct knee bend, a traditional method still produces a very good starting
point: With your bike mounted level in a trainer, sit square on the saddle while wearing
your cycling shorts and shoes. Put your heels on the pedals. Pedal backwards. Adjust
saddle height till your knees straighten but hip movement is minimal. Then when you clip
in, knee bend will be on the money. You can also check this on a ride by pedaling with
your heels (not when there's traffic, of course).

The benefit of a bike custom built for your body dimensions is not to automatically put
you in a perfect position, but to put you in a "fit window" of 1-2 cm. Then you can tweak
things to maximize comfort and pedaling efficiency.

When all is said and done, your riding position should put 60% of your weight on the
back wheel and 40% on the front. This is important for bike control as well as comfort.

Fit is not static! Stay aware of how your body reacts to riding and make position
improvements as necessary. Various things affect fit over time, including simply getting
older and losing flexibility.

IV. Frame building techniques. This
detailed critique on frame building will give those interested
even deeper insight into how all those measurements come together and translate into
bike performance.

Now for a few questions whose answers may help reinforce these ideas.

Q. I am a new rider and still in the Hybrid ranks with my
1989 Schwinn Crisscross. I recently did a two day 150 mile
charity ride (second year on the same bike) and felt pretty good. I did ride
extensively and did light weight training, spin classes during the week,
weekend rides - anywhere from 20 - 40 miles on Saturday and Sunday. I maintained
this regime for about 3.5 months prior to the ride. So I would consider
myself in pretty good shape.

My question is the riders I rode with in the ride were in marginal shape -
however they both had brand new road bikes. One had the Lemond -Alp Duez and
the other had a FELT. Prior to the ride I found I was working doubly
hard to keep the pace when we went out on training rides. In fact on one
ride I hung with a group of 7 with road bikes for about 30 miles and I
seemed to be the only one sweating. I weigh 210 and the other riders were
about the same weight. However they finished a good 40 minutes ahead of
me. My bike weighs approximately 25 lbs. - can the bike make that much
difference in the ride? I am feeling a little blue today because I thought I was
going to do much better. - TZ

A. Weight does make a difference, especially in the pedals and wheels
as you are continuously accelerating and decelerating as you ride
and the inertial resistance to acceleration is a big energy drain.
And the geometry, rather than the weight, of the frame is a large factor as well.
It is not the 5 pounds in the frame itself (which could easily be in two
water bottles instead).

Q. I usually do road rides of 50 miles with 3M to 4M feet of elevation and
I wear Sidi Bullet, (@ 650 grams), which are mountain bike shoes. Climbing is my weakness.
Would I see any improved performance if I started wearing lighter and stiffer road bike
shoes, such as the Sidi Genius 5.5 HT Carbon, (@ 540 grams)? NT

A. The weight in pedals, cranks, chain, and rims/tires (which has angular
inertia when you are accelerating - something you are doing all the time even when
on the flats) is much more important weight than in the frame, your water bottle,
etc. The decrease in weight of these shoes might make some difference in climbing.
But the stiffness or other design features would not. I once had a fellow at a local bike
shop tell me that all he did was buy lighter rims - he biked a lot - and yet it allowed
him to ride another 10 miles before he got to his usual level of fatigue.